Drive shafts are used to transfer rotational motion. In trucks and automobiles, drive shafts can be used to transfer the rotation motion generation by the engine. Drive shafts can be used in machines such as rolling mills and printing presses to transfer the motion generated by the motor to various of the operational components.
A drive shaft is a tubular or solid shaft member which has been provided at one end with means for coupling to a rotating drive source and at the other end with means for couple to a driven component. Frequently a tube yoke is provided to one end, and a slip stub shaft is provided at the other end to slidably engage a slip yoke. Most commercial drive shafts are formed from three components, a tubular shaft member and two end configurations.
Drive shafts come in a variety of sizes and may vary from small shafts used in small machines to the shafts used in small lawn tractors to the very large drive shafts used in large trucks and off the road vehicles.
During service the individual components of a drive shaft will be subject to wear and corrosion, and may be accidentally damaged. Because the individual components, and in particular, the end configuration, are expensive precision items it is cost effective to save those components which have not been worn excessively and remain operative. For this reason it is frequently desired to disassemble a drive shaft to salvage or replace one or more of the components.
A drive shaft can be disassembled by cutting the welds, holding the ends onto the shaft, and then through application of a tensile load removing one or both ends.
A drive shaft is assembled by pressing and subsequently welding onto a tubular shaft member, end components having the desired configurations.
The efficiency with which a drive shaft transmits rotational motion and the rate of wear are a function of the balance and alignment of the drive shaft. If a drive shaft is out of balance excessive vibration will result. Excessive vibration which can cause excessive wear in the drive train components including the differential and transmission. Further an unbalanced drive shaft can cause vibrations in the vehicle and be noisy.
To assemble a drive shaft one or both replacement ends are placed in contact with the shaft, the shaft is secured, the ends are aligned with respect to the shaft axis, and a force is applied to press the ends onto the shaft. If the shaft and the end configurations are not properly aligned the components will not have a common axis of rotation. This can lead to inefficient transfer of rotational motion and excessive wear and vibration. To assure that the individual components are aligned each component should be aligned with respect to a common axis of rotation. If each component is aligned with respect to the same axis then all components would be aligned with respect to each other and the resulting shaft will transfer motion in an efficient manner.
Using most of the current processes for the assembly of three piece drive shafts each end configuration must be separately affixed and aligned to the shaft. Many of the machines require that the shaft be secured to a bed, the end configuration be placed in a jig pressed on to the shaft and then for the second end configuration to be positioned the shaft must be removed from the bed, turned end for end and process repeated, the second end configuration placed in the appropriate jig aligned with respect to the shaft and pressed onto the shaft. This operation which requires securing the shaft for each end configuration needs to be pressed on, can be time consuming and can lead to errors of alignment, the shaft has to be positioned and secure for each end.
The process for disassembling and assembling drive shafts is time consuming. The time to disassemble the main drive shaft for a ten wheel dump truck, such drive shaft having an outside diameter of 4.095 inches with a wall thickness of 0.180 inches, and a length between about 48 inches, and having a 1710 series tube yoke, and a 1710 series stub shaft about 45 minutes using conventional technology. The accuracy with which drive shafts can be aligned using conventional technology, the alignment can vary by 3/16 and 1/4.
The efficiency with which the rotational force of the driving element is transferred to the driven element, is in addition to being a function of the drive shaft components, a function of the weld configurations. If the axis of rotation of the end configuration and the shaft are not common the shoulder of the end configuration may not be parallel to a plane perpendicular to the shaft axis. This can result in a variable separation between the end of the tube shaft and the collar of the end configuration. Such variation in the separation between the end configuration shoulder and the tube shaft can lead to a variation in weld metal volume around the circumference of the shaft. This variation in volume of weld around the circumference of the shaft will cause a variation in weight as a function of circumferential position which can unbalance the drive shaft.
To compensate for the variations in circumferential weight subsequent to assembly the drive shaft must be balanced by the placement of steel weights attached to the shaft. The steel weights increase the weights increase the weight of the drive shaft and thereby decreasing its efficiency and also add asymmetry to the weight distribution which can contribute to the ware.
Several patents are directed to methods and equipment for use in the assembly and disassembly of drive shafts. Among these are U.S. Pat. No. 4,571,807 entitled DRIVESHAFT REBUILDING MACHINE of Gordon E. Heinz, Arthur W. Henke and Vernon J. Burzan. The '807 patent teaches a drive shaft rebuilding machine for installing an end piece on a drive shaft tube. The machine is provided with centering clamps for positioning and securing the drive shaft tube. End components are secured in a fixture on the shaft tube or jig which firmly engages a conventional yoke and/or spline and can be moved so as to align the end piece with respect to the drive shaft tube. The end configuration is pressed into the drive shaft tube by means of a hydraulic cylinder. The device of the '807 patent is provided with multiple rotating crank mechanisms for manually adjusting and aligning of the drive shaft tubes. The machine of the '807 patent centers the shaft by means of tapered side support members that are cranked in to firmly engage the shaft. Depending on the skill of the operator and the force with which he turns the crank it is possible to distort the shaft and or to place a slight warp in the shaft. Further if the shaft is grasped when the shaft is rotated with respect to the clamps and held too tightly the pressing operation which is used to place the fixtures into the shaft could cause further distortion of the shaft.
U.S. Pat. No. 3,758,098 entitled MACHINE FOR WORKING DRIVE SHAFTS of Mark Vrialakas teaches a machine for working simultaneously on both the head stock and tail stock of an automobile drive shaft by applying a compressive load to the drive shaft tube in combination with the end pieces. The head and tail stock are held in position by clamping studs. A special complimentary yoke is used to engage the universal. A set screw is provided to hold the hub of the complimentary yoke into a recess in a collar. The machine of the '098 patent permits only limited adjustment with respect to centering the head and tail stocks and allows for only limited variability with respect to shaft diameter, and with respect to head and tail stock configuration. The machine of the '098 patent requires multiple manual operations to align the shaft. Since the machine relies on manual adjustments for centering the components the accuracy with which a drive shaft can be aligned depends on the operator.
U.S. Pat. No. 3,880,416 entitled FIXTURE ASSEMBLY FOR REPAIR OF UNIVERSAL JOINTS of Don A. Horwitz teaches a fixture hold for securing a drive shaft tube and yoke end pieces. The fixture uses a plurality of vise rod, or bolts, for alignment. Since the device requires manual adjustment the alignment will depend on the skill of the operator and the time required to center the yoke with respect to a drive shaft can be extensive.
U.S. Pat. No. 4,459,727 entitled MACHINE FOR FABRICATING DRIVESHAFTS of Robert Burton and Glenn Parma teaches a machine for fabricating drive shafts. The tail stock is positioned and supported by a centering spindle, and the head stock is positioned and supported by a drive spindle. Rotatable locking face plates are used for mounting the spindles. Since alignment of the drive shaft is accomplished by the manual adjustment the alignment depends on the operator and the alignment process is time consuming.
In addition, to the drive shaft rebuilding machines described in the above referenced patents, several manufacturers offer machines for use in the rebuilding and disassembly of drive shafts. For example, Rockwell offers a Cut-Pull-Push-Yoke machine which is provided with a bed and a jig for holding and positioning one end. Using the Rockwell Cut-Pull-Push-Yoke machine only one end configuration at a time can be positioned and pushed into the drive shaft tube. Since the drive shaft must be removed and repositioned after the first end is pressed onto the tube if a second end is to be pressed onto the tube the alignment will depend upon the skill of the operator in repositioning the shaft and the time for assembling a drive shaft with two end configurations will be extended by the time required to remove the shaft, rotate the shaft and reaffix the shaft to the bed.
Axiline Precision Products Company offers a DRIVE LINE BALANCER for use in the assembly and disassembly of drive shafts. The DRIVE LINE BALANCER is provided with a centering ring which has three manually adjusted centering screws. The drive shaft is placed through the centering ring and the shaft is aligned by movement of the centering screws. A chuck, which can be manually aligned, is provided with a variety of fixtures for use in positioning the end configuration. By changing the fixture it is possible to position chucks of varying sizes and configurations. The machine offered by Axiline requires a variety of manual adjustments and only one end of the drive shaft can be worked on at a time.
Using conventional technology the time required for disassembling and assembling drive shafts is extensive and proper alignment requires a skilled operator. As with any job that relies on operator skill there will be a distribution of quality.
A drive shaft rebuilding machine which can accurately align the end configurations with respect to the axis of the tube shaft and thus provide a drive shaft with improved alignment and better balance when compared to prior assembly techniques can be of value.
Significant savings could be realized from the improved efficiency with which rotational motion could be transferred, the longer life of the drive shaft and the components in the drive train, and the reduced time and material required for post assembly balancing.
There is a need for a machine which has sufficient versatility, that it can readily assemble and disassemble drive shafts having a variety of different shaft sizes and end configurations.
There is a need for a drive shaft machine which will allow for the alignment of the end components with a minimum of operator input, with a high degree of reproducibility, and with a reduction in the time required for the assembly and/or disassembly.
Because the tube shaft and/or the end configurations may need to be modified or replaced, a machine which in a cost effective manner can disassemble and then reassemble a drive shaft can have value.
Further, because small shops frequently are called on to rebuild drive shafts having a variety of end configurations, shaft diameters and shaft lengths there is a need for a universal machine which can readily assemble and disassemble drive shafts of various sizes, having varying end configurations.
The present invention is directed to a machine which will allow drive shafts having different lengths, diameters, and end configurations to be quickly, accurately, reproducibility; and easily disassembled, aligned and assembled.